Since a lubricant which is used ina chain, a roller chain, a chain conveyor, a bearing and the like is exposed to a high temperature, an amount of a lubricant evaporated greatly influences a life of an apparatus. Thus, a lubricant loses an ordinary viscosity under a condition of a high temperature and becomes a thin film, so that an amount of a lubricant evaporated has to be controlled under severer conditions. As an ordinary lubricant for a high temperature, high-molecular oil with a high viscosity has been used to control an amount evaporated. Although an amount of such oil evaporated is small, a power loss is great, and it is undesirable in view of a total performance of a lubricant. Further, when such oil is exposed to a thin film and a high temperature, a residual amount is large, but it is solidified. Not only are characteristics as a liquid lost, but also it becomes a solidified sludge to prevent flow of oil, inviting poor lubrication of a lubricating portion. Accordingly, a lubricant for a high temperature of which the amount evaporated in a thin film at a high temperature is controlled and of which the fluidity is maintained for a long period of time has been in demand.
From this standpoint, the present invention has been made, and it aims to provide a lubricant composition for a high temperature of which the amount evaporated in a thin film at a high temperature is controlled and of which the fluidity is maintained for a long period of time.